Hong Kong Trail – Runners looking for nice views that get them away from all those skyscrapers can try a seven-kilometer stretch of the Hong Kong Trail that begins at Victoria Peak and finishes at Pokfulam Reservoir.

Riverwalk (Chattanooga, Tennessee) – The 20-kilometer Riverwalk is a linear park that starts at Ross's Landing in Chattanooga and finishes in the city center.

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Photos:World's best city jogging trails

Yoyogi Park (Tokyo) – Though temporarily closed, Tokyo's Yoyogi Park is usually open 24 hours a day, making it a popular destination for those in need of a post-work run.

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Story highlights

A baseline of fitness requires about four hours of exercise a week

Running about 35 miles a week will train you for a half or full marathon

You can also cross-train, do speed workouts, run hills and weight lift

John Farah is the co-author of "Let's Pick it up a Bit," a memoir and a guide to help people lead an active life. He has run more than 430 races, including 123 marathons.

Pick someone you know -- anyone at all -- and ask them this simple question: "Do you work out?"

This time of year, the answer will usually be "yes."

It is in vogue to exercise and even more in vogue to run. But with New Year's resolutions quickly fading, the real question is this: How do you turn a fad into a lasting, meaningful habit and a healthy lifestyle?

Four

To establish a minimum baseline of fitness, a person needs to exercise about four hours a week.

Four hours per week is 240 minutes. Not bad, right? That's a lot less time than most of us spend watching TV. Even better, you can break that down any way you want.

If you work out 40 minutes per day, six days a week, you got it. Or if you prefer, make it 60 minutes a day, four times a week. The choice is yours.

There's also flexibility in the type of exercise you do. If you'd like to improve as a runner, then of course you should focus on running. But if you'd simply like to get in shape, you can do almost anything -- yoga, swim, bike, lift weights, go for a brisk walk or even work in the garden.

Twelve

By now, you probably get the drift.

To take fitness to the highest level possible, you have to increase your weekly time commitment to 12 hours. That boils down to two hours a day, six days a week.

At this point, you'll also need to develop a rigorous, precise training plan, whether you'd like to focus on running or a full-body approach. We're talking cross-training, speed workouts, longer runs, hill runs, yoga and weight lifting, among other things.

With that kind of effort, you'll be in the top 10% of your age group. Running marathons will be second nature. Fitness won't be a fad -- it'll be a lifestyle.

Yes, it is a lot of time. Yes, it's a major commitment. But if you want that New Year's resolution to really translate into a New You that's here to stay, that's what it'll take.